Sodoku, More Than You Wanted to Know

I've come across the word once or twice of late, and I saw a book of sodoku in a Wal-mart recently, but in the few seconds I could spare to look it over, I found no enlightenment. If you're like me, you'll read this article and say, "Ohhhh, now I know what Sodoku is." Turns out I already did know, but by another name. I used to skip them regularly in the Dell crosswords I would pick up in the '80s.

Update: As most of us now realize, the word is Sudoku, not Sodoku. I'm getting used to the embarrassment.